The string viewer in 9.5.3 has changed to include the scroll bar unless the string viewer box is about 50 characters long. This has really messed up all my dashboards. Is there a way to disable this or fix the problem?
I would suggest opening a support ticket then to investigate this further then. There a number of known issues with dashboards in APM 95x and the support team should be able to review your Webview/Webstart logs.